1. Field of the Invention
The present invention relates to a fuel pump adapted to suck in and pressurize a fuel such as gasoline and discharge the pressurized fuel.
2. Discussion of Related Art
There is known a fuel pump adapted to suck in and discharge a fuel by rotating an impeller in a pump casing. An example of this type of fuel pump is disclosed in Published Japanese Translation of PCT International Publication No. Hei 9-511812. The impeller rotating in the pump casing has an approximately disk-shaped configuration. A group of recesses are formed in a region extending along the outer peripheries of the obverse and reverse sides of the disk-shaped impeller. The recesses are repeatedly arranged in the circumferential direction with a partition provided between each pair of adjacent recesses. The radially outer end face of each recess extends parallel to the axis of rotational symmetry of the impeller. The impeller is rotated at high speed about the axis by a motor.
The lifetime of fuel pumps is mostly determined by the progression of wear between the commutator and brush of the motor. The wear progression rate is closely related to the motor current value. That is, the smaller the motor current, the lower the wear progression rate. For this reason, there is a demand that the lifetime of fuel pumps should be extended by increasing the pump efficiency and reducing the motor current to thereby lower the wear progression rate.
With the technique disclosed in the above-mentioned Publication No. Hei 9-511812, the partition for separating each pair of adjacent recesses is inclined rearward in the direction of rotation as the distance from the obverse and reverse sides of the impeller increases inward in the direction of thickness of the impeller, thereby increasing the pump efficiency.